Driving apparatus, semiconductor apparatus, and driving method

ABSTRACT

A driving apparatus includes: a driving section configured to drive a control terminal of a semiconductor device according to a control signal input from an outside, the semiconductor device including a first main terminal, a second main terminal, and the control terminal that is configured to control a connection state between the first main terminal and the second main terminal that are connected in parallel with a snubber; and a drive control section configured to lower a drive capability of the driving section during a period in which an inter-main-terminal voltage between the first main terminal and the second main terminal changes by a predetermined reference voltage difference owing to switching of the semiconductor device, compared with other at least some periods.

The contents of the following Japanese patent application areincorporated herein by reference:

-   No. 2020-205998 filed in JP on Dec. 11, 2020

BACKGROUND 1. Technical Field

The present invention relates to a driving apparatus, a semiconductorapparatus, and a driving method.

2 Related Art

In a power apparatus such as a voltage type inverter including asemiconductor switching device (hereinafter, also referred to as“semiconductor device”) such as a metal oxide semiconductor field effecttransistor (MOSFET) or an insulated gate bipolar transistor (IGBT),high-frequency voltage and current vibrations are generated when thesemiconductor device is switching at a high speed. Patent Literature 1discloses a vibration suppression circuit 20 added to the outside of ahousing 10 of a semiconductor apparatus 100 (paragraph 0018, FIG. 1A,FIG. 1B, FIG. 2, and the like). Patent Literature 2 describes that aresistance value between a control electrode and an output node of asemiconductor switching device is switched to a different value betweena case where the semiconductor switching device is turned on and a casewhere the semiconductor switching device is turned off (claim 1).

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Patent No. 6597902-   Patent Literature 2: WO 2017/026367

In recent years, the performance of semiconductor devices has beenimproved, and high-speed switchable semiconductor devices such asSiC-MOSFETs have also been realized. Therefore, it is desirable torealize a driving system capable of suppressing vibration of thesemiconductor device with a low loss even in a case where thesemiconductor device is switched at a high speed.

SUMMARY

A first aspect of the present invention provides a driving apparatus.The driving apparatus may include a driving section configured to drivea control terminal of a semiconductor device according to a controlsignal input from an outside, the semiconductor device including a firstmain terminal, a second main terminal, and the control terminal that isconfigured to control a connection state between the first main terminaland the second main terminal that are connected in parallel with asnubber. The driving apparatus may include a drive control sectionconfigured to lower a drive capability of the driving section during aperiod in which an inter-main-terminal voltage between the first mainterminal and the second main terminal changes by a predeterminedreference voltage difference owning to switching of the semiconductordevice, compared with other at least some periods.

In a period in which the semiconductor device is turned off, the drivecontrol section may drive the control terminal at a first drivecapability by the driving section while the inter-main-terminal voltageis less than a first threshold. In a period in which the semiconductordevice is turned off, the drive control section may drive the controlterminal at a second drive capability higher than the first drivecapability by the driving section when the inter-main-terminal voltagebecomes equal to or higher than the first threshold.

In a period in which the semiconductor device is turned on, the drivecontrol section may drive the control terminal at a third drivecapability by the driving section while the inter-main-terminal voltageis equal to or higher than a second threshold. In a period in which thesemiconductor device is turned on, the drive control section may drivethe control terminal at a fourth drive capability lower than the thirddrive capability by the driving section when the inter-main-terminalvoltage becomes less than the second threshold.

The first threshold and the second threshold may be 60% or more and lessthan 100% of the inter-main-terminal voltage in a steady state in whichthe semiconductor device is turned off.

The first threshold and the second threshold may be 80% or more and lessthan 95% of the inter-main-terminal voltage in a steady state in whichthe semiconductor device is turned off.

The first threshold and the second threshold may be the same value.

The drive control section may change a drive capability of the controlterminal by changing at least one of a magnitude of a resistance of aresistor connected between the control terminal and a referencepotential or a capacitance of a capacitor connected between the controlterminal and the first main terminal or the second main terminal.

The driving section may include a plurality of driving circuits in whicha resistor or a capacitor and a driving switch are each connected inseries between a reference potential and the control terminal. The drivecontrol section may change a drive capability of the driving section byswitching the driving switch of each of the plurality of drivingcircuits.

The semiconductor device may be a SiC-MOSFET or a SiC-IGBT.

In a second aspect of the present invention, a semiconductor apparatusis provided. The semiconductor apparatus may include a semiconductordevice and a driving apparatus that is configured to drive a controlterminal of the semiconductor device.

In a third aspect of the present invention, a driving method isprovided. A driving method may include driving, by a driving section, acontrol terminal of a semiconductor device according to a control signalinput from an outside, the semiconductor device including a first mainterminal, a second main terminal, and the control terminal that isconfigured to control a connection state between the first main terminaland the second main terminal that are connected in parallel with asnubber. The driving method may include lowering a drive capability ofthe driving section during a period in which an inter-main-terminalvoltage between the first main terminal and the second main terminalchanges by a predetermined reference voltage difference owning toswitching of the semiconductor device, compared with other at least someperiods.

Note that the above summary of the invention does not enumerate all ofthe features of the present invention. Further, a sub-combination ofthese feature groups can also be an invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a configuration of a power apparatus 100 according tothe present embodiment together with a load 140.

FIG. 2 illustrates a configuration of the power apparatus 100 accordingto a modification of the present embodiment together with the load 140.

FIG. 3 illustrates an example of transient changes in current andvoltage at the time of turn-on of a semiconductor device.

FIG. 4 illustrates an example of transient changes in current andvoltage at the time of turn-off of the semiconductor device.

FIG. 5 illustrates a configuration of a semiconductor apparatus 115according to the present embodiment.

FIG. 6 illustrates an operation waveform at the time of turn-off of thesemiconductor device.

FIG. 7 illustrates an operation waveform at the time of turn-on of thesemiconductor device.

FIG. 8 illustrates an example of transient changes in current andvoltage at the time of turn-off of the semiconductor device.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, the present invention will be described through embodimentsof the invention, but the following embodiments do not limit theinvention according to the claims. In addition, not all combinations offeatures described in the embodiments are essential to the solution ofthe invention.

FIG. 1 illustrates a configuration of a power apparatus 100 according tothe present embodiment together with a load 140. The load 140 is amotor, an electric machine, or another power-consuming apparatus thatoperates by receiving power supply from the power apparatus 100. Thepower apparatus 100 includes an electrolytic capacitor 110, asemiconductor apparatus 115, an inductor 150, and a snubber 180.

The electrolytic capacitor 110 is connected between a positive bus barand a negative bus bar of the power apparatus 100, and functions as avoltage source of the semiconductor apparatus 115 and the load 140. Theelectrolytic capacitor 110 accumulates a power supply voltage suppliedfrom a power source (not illustrated) between the positive bus bar andthe negative bus bar, and supplies the power supply voltage to thesemiconductor apparatus 115.

The semiconductor apparatus 115 includes one or more semiconductordevices 120 a and 120 b (also referred to as “semiconductor device 120”)and one or more driving apparatuses 130 a and 130 b (also referred to as“driving apparatus 130”). In the present embodiment, for the convenienceof explanation, a case where the semiconductor apparatus 115 includestwo semiconductor devices 120 and two driving apparatuses 130 will bedescribed, but the semiconductor apparatus 115 may include one or threeor more semiconductor devices 120 and driving apparatuses 130. Thesemiconductor apparatus 115 may be a semiconductor module in which oneor more semiconductor devices 120 and one or more driving apparatuses130 are integrated by resin sealing or the like.

Each semiconductor device 120 is a semiconductor switch device such as aMOSFET or an IGBT. Each semiconductor device 120 may be a SiC-MOSFET ora SiC-IGBT capable of switching at a higher speed. Each semiconductordevice 120 includes a first main terminal, a second main terminal, and acontrol terminal that controls a connection state between the first mainterminal and the second main terminal. In a case where the semiconductordevice 120 is a MOSFET, the semiconductor device 120 includes a drainand a source as the first main terminal and the second main terminal,and includes a gate as the control terminal. In a case where thesemiconductor device 120 is an IGBT, the semiconductor device 120includes a collector and an emitter as the first main terminal and thesecond main terminal, and includes a gate as the control terminal. Inthe present embodiment, for the convenience of explanation, a case wherethe semiconductor device 120 is a MOSFET will be described. In thesemiconductor devices 120 a and 120 b, the main terminals are connectedin series between the positive bus bar and the negative bus bar in thisorder.

The driving apparatuses 130 a and 130 b are provided corresponding tothe semiconductor devices 120 a and 120 b, respectively. Each drivingapparatus 130 is connected to the control terminal of the correspondingsemiconductor device 120, and drives the control terminal according to acontrol signal input from the outside. In this drawing, the drivingapparatuses 130 are provided individually for the semiconductor devices120, but the plurality of driving apparatuses 130 may be collectivelyreferred to as a “driving apparatus”.

The inductor 150 is connected in series with the load 140 between thepositive bus bar and an intermediate terminal that is between thesemiconductor device 120 a and the semiconductor device 120 b. Thesnubber 180 is connected between the positive bus bar and the negativebus bar outside the semiconductor apparatus 115. Accordingly, thesnubber 180 is connected in parallel with the first main terminal andthe second main terminal of each semiconductor device 120 between thepositive bus bar and the negative bus bar. The snubber 180 suppressesvibrations in voltage and current due to switching of the semiconductordevice 120. In the present embodiment, the snubber 180 is, for example,an RC snubber, and may include a resistor 185 and a capacitor 190connected in series between the positive bus bar and the negative busbar.

The operation of the power apparatus 100 in this drawing is as follows.First, in response to a control signal from the outside, the drivingapparatuses 130 a and 130 b drive the semiconductor device 120 a to beturned off and the semiconductor device 120 b to be turned on. As aresult, a current flows from the positive side of the electrolyticcapacitor 110 to the negative side of the electrolytic capacitor 110 viathe inductor 150, the load 140, and the semiconductor device 120 b,power is supplied to the load 140, and energy is stored in the inductor150.

Next, in response to a control signal from the outside, the drivingapparatuses 130 a and 130 b drive the semiconductor device 120 a to beturned on and the semiconductor device 120 b to be turned off. Theinductor 150 keeps flowing of a current by the stored energy, andperforms a freewheeling operation in which the current output from theinductor 150 is returned to the inductor 150 via the load 140 and thesemiconductor device 120 a. When the power supplied to the load 140 isattenuated, the driving apparatuses 130 a and 130 b receive a controlsignal from the outside, and turn off the semiconductor device 120 a andturn on the semiconductor device 120 b.

FIG. 2 illustrates a configuration of a power apparatus 100 according toa modification of the present embodiment together with the load 140. Thepower apparatus 100 in FIG. 2 is the same as the power apparatus 100 inFIG. 1 except that a plurality of snubbers 280 a and 280 b (alsoreferred to as “snubber 280”) are provided instead of the snubber 180.Thus, members having the same or similar functions and configurationsare denoted by the same reference numerals, and description thereof isomitted except for differences.

In the present modification, the snubbers 280 are provided correspondingto the semiconductor devices 120 and connected between main terminals ofthe corresponding semiconductor devices 120, respectively. Accordingly,each snubber 280 is connected in parallel to the first main terminal andthe second main terminal of the corresponding semiconductor device 120.In the present modification, the snubber 280 a is, for example, an RCsnubber, and may include a resistor 285 a and a capacitor 290 aconnected in series between main terminals of the correspondingsemiconductor device 120. Likewise, the snubber 280 b is also an RCsnubber as an example, and may include a resistor 285 b and a capacitor290 b connected in series between main terminals of the correspondingsemiconductor device 120.

In FIG. 1 and FIG. 2, instead of the semiconductor device 120 a, arectifier diode having a cathode on the positive bus bar side and ananode on the intermediate terminal side may be used. The rectifier diodemay be a SiC diode capable of switching at a high speed as an example.

FIG. 3 illustrates an example of transient changes in current andvoltage at the time of turn-on of the semiconductor device. This drawingis an excerpt of FIG. 5 of Patent Literature 1. “Comparative example”,“first example”, and “second example” in this drawing refer to thecomparative example, the first example, and the second example in PatentLiterature 1, but do not refer to the comparative example and examplesin the specification of the present application.

The “comparative example” indicates a transient change in a collectorcurrent I_(C) (that is, a current flowing between the main terminals)and a collector-emitter voltage V_(CE) (that is, a voltage between themain terminals) in a case where the “semiconductor apparatus 100” ofPatent Literature 1 does not include the “vibration suppression circuit20”. The “first example” indicates a transient change in the currentI_(C) and the voltage V_(CE) in a case where the “semiconductorapparatus 100” of Patent Literature 1 includes the “vibrationsuppression circuit 20” having the same connection relationship as thatof the snubber 180 in FIG. 1 of the present application. The “secondexample” indicates a transient change in the current I_(C) and thevoltage V_(CE) in a case where the “semiconductor apparatus 110” ofPatent Literature 1 includes a plurality of “vibration suppressioncircuits 20” having the same connection relationship as that of eachsnubber 280 in FIG. 2 of the present application (paragraph 0049 ofPatent Literature 1).

As illustrated in this drawing, in the “comparative example” in whichthe “vibration suppression circuit 20” is not added to the“semiconductor apparatus 100”, the current I_(C) and the voltage V_(CE)greatly vibrate at the time of turn-on of the “semiconductor device14a”. On the other hand, in the “first example” and the “second example”in which the “vibration suppression circuit 20” is added to the“semiconductor apparatus 100”, the vibrations of the current I_(C) andthe voltage V_(CE) are suppressed at the time of turn-on of the“semiconductor device 14a”. The “vibration suppression circuit 20” ofPatent Literature 1 suppresses the vibrations of the current I_(C) andthe voltage V_(CE) likewise also at the time of turn-off of the“semiconductor device 14a”. In FIG. 5 of Patent Literature 1, thevoltage V_(CE) indicates the voltage between the main terminals of the“semiconductor device 15a” on the opposite side in a case where the“semiconductor device 14a” is turned on (see paragraph 0049).

FIG. 4 illustrates an example of transient changes in current andvoltage at the time of turn-off of the semiconductor device 120 b. Thisdrawing illustrates changes in the drain current Id and the drain-sourcevoltage Vds in a case where a SiC-MOSFET is used as an example of thesemiconductor device 120 b in the power apparatus 100 of FIG. 1. In theexample of this drawing, the semiconductor module of 1200 V/200 A istargeted, and a wiring inductance Ls1 between the electrolytic capacitor110 and the snubber 180 in FIG. 1 is 20 nH, a wiring inductance Ls2between the snubber 180 and the semiconductor devices 120 a and 120 b inthe semiconductor apparatus 115 is 5 nH, a resistance Rs of the resistor185 is 0.5Ω, a capacitance Cs of the capacitor 190 is 50 nF, and aresistance (gate resistance) between the driving apparatus 130 b and thesemiconductor device 120 b is 0.1Ω and constant.

The wiring inductance Ls2 exists between the semiconductor devices 120 aand 120 b and the snubber 180. In addition, each semiconductor device120 has a junction capacitance (denoted as “Cos”) between the drain andthe source. Therefore, the semiconductor apparatus 115 includes, on theside closer to the semiconductor apparatus 115 than to the snubber 180,an LC circuit in which the inductance Ls2 and the junction capacitanceCos are connected in series. Here, the wiring inductance Ls2 can bereduced by shortening the wiring by bringing the snubber 180 as close aspossible to the semiconductor devices 120 a and 120 b. However, sincethe snubber 180 is provided outside the package of the semiconductorapparatus 115 and the semiconductor devices 120 a and 120 b have acertain size, there is a limit to suppressing the wiring inductance Ls2.

Such an LC circuit with the inductance Ls2 and the junction capacitanceCos causes local fluctuations in the current Id and the voltage Vds thatcannot be sufficiently suppressed by the snubber 180 or the snubber 280farther away from the semiconductor devices 120 a and 120 b. In thisdrawing, the semiconductor device 120 b is turned off at the time of15.0 μs on the horizontal axis, but large variations in current andvoltage at a relatively high frequency occur for a short period of timeat this timing as compared with the vibrations in current and voltage inFIG. 3.

Here, in order to suppress the local vibration as illustrated in FIG. 3caused by the LC circuit due to the inductance Ls2 and the junctioncapacitance Cos, it is considered to provide a damping resistor Rd inseries with the LC circuit. A damping coefficient ζ in a case where sucha damping resistor Rd is provided is expressed by the followingExpression (1).

ζ=Rd/2·√(Cos/Ls2)  (1)

As the damping coefficient ζ is larger, the vibration by the LC circuitcan be greatly attenuated. From this viewpoint, the damping coefficientζ may be 0.8 to 1.0 or more. Also in a case where the snubber 180 or thesnubber 280 is provided outside the semiconductor apparatus 115, thesnubber 180 or the snubber 280 is disposed as close as possible to thesemiconductor apparatus 115 in the power apparatus 100. Therefore, theinductance Ls1 can be several times to several tens of times or more theinductance Ls2. As it is clear from Expression (1), the dampingcoefficient ζ is proportional to −½ power of the inductance. Therefore,in order to suppress the resonance of the LC circuit due to theinductance Ls1+Ls2 and the junction capacitance Cos by the dampingresistor Rd without providing the snubber 180 or the snubber 280, it isnecessary to set the damping resistor Rd to several times to severaltens of times or more in order to realize the damping coefficient ζ ofthe same magnitude. For example, in a case where Ls1+Ls2 is 16 timesLs2, the damping resistor Rd has to be 4 times in order to realize thesame damping coefficient ζ.

Here, a switching loss Psw, which is energy (or power) lost duringswitching of the semiconductor device 120 b, is a product of a current(for example, drain current) Id flowing between the main terminals ofthe semiconductor device 120 b during switching, an inter-main-terminalvoltage (for example, drain-source voltage) Vds of the semiconductordevice 120 b, and a switching time Tsw. Here, assuming that theswitching loss Psw is generated by the damping resistor Rd,Psw=Vd×Id=Rd×Id²×Tsw. Therefore, the damping resistor Rd is expressed bythe following Expression (2).

Rd=Psw/(Id ²)/Tsw  (2)

From Expression (2), it can be seen that the switching loss Psw of thesemiconductor device 120 b increases when the damping resistor Rd isincreased. Therefore, in a case where the resonance of the LC circuit issuppressed by the damping resistor Rd without providing the snubber 180and the snubber 280, the switching loss Psw increases as the dampingresistor Rd increases.

Therefore, the power apparatus 100 suppresses the vibration asillustrated in FIG. 3 using the snubbers such as the snubber 180 of FIG.1 and the snubber 280 of FIG. 2, and also causes the semiconductordevice 120 to generate the switching loss Psw that generates the dampingresistor Rd for realizing the damping coefficient ζ to some extent so asto attenuate the local vibration generated by the LC circuit due to theinductance Ls2 and the junction capacitance Cos.

FIG. 5 illustrates a configuration of a semiconductor apparatus 115according to the present embodiment together with the electrolyticcapacitor 110. The semiconductor apparatus 115 suppresses localvibrations caused by the LC circuit due to the inductance Ls2 and thejunction capacitance Cos in the power apparatus 100 to which a snubbersuch as the snubber 180 of FIG. 1 or the snubber 280 of FIG. 2 is addedas an example.

In this drawing, the members denoted by the same reference numerals asthose in FIG. 1 or FIG. 2 have the same functions and configurations asthose of the corresponding members in FIG. 1 or FIG. 2, and thus thedescription thereof will be omitted except for the differences. Asillustrated in FIG. 1 and FIG. 2, the semiconductor apparatus 115includes one or more semiconductor devices 120 and one or more drivingapparatuses 130. In this drawing, the description will be given focusingon one semiconductor device 120 (for example, the semiconductor device120 b) and one driving apparatus 130 (for example, the driving apparatus130 b).

The driving apparatus 130 includes a driving section 500 and a drivecontrol section 530. The driving section 500 receives control accordingto a control signal input from the outside from the drive controlsection 530, and drives the control terminal of the semiconductor device120 according to the control signal. The driving section 500 includes adriving circuit in which a resistor 510 a and a driving switch 520 a areconnected in series, and a driving circuit (a driving circuit on thenegative side) in which a resistor 510 b and a driving switch 520 b areconnected in series, between the negative bus bar serving as a negativereference potential and the control terminal of the semiconductor device120. In addition, the driving section 500 includes a driving circuit inwhich a resistor 510 c and a driving switch 520 c are connected inseries, and a driving circuit (a driving circuit on the positive side)in which a resistor 510 d and a driving switch 520 d are connected inseries, between the positive bus bar serving as a positive referencepotential and the control terminal of the semiconductor device 120. Inthe example of this drawing, the driving switches 520 a and 520 b arep-channel MOSFETs, and the driving switches 520 c and 520 d aren-channel MOSFETs. Alternatively, each of the driving switches 520 a to520 d (also referred to as “driving switch 520”) may be any switchingdevice capable of connecting or disconnecting between the controlterminal of the semiconductor device 120 and the positive bus bar or thenegative bus bar via each of the resistors 510 a to 510 d (also referredto as “resistor 510”).

The drive control section 530 controls the driving section 500 accordingto a control signal input from the outside. Here, during a period inwhich an inter-main-terminal voltage between the first main terminal andthe second main terminal of the semiconductor device 120 changes by apredetermined reference voltage difference when the semiconductor device120 is switching, the drive control section 530 performs control tolower the drive capability of the driving section 500 as compared withat least some other periods. In the present embodiment, the drivecontrol section 530 switches the driving switch 510 of each of theplurality of driving circuits to change the drive capability of thedriving section 500.

The drive control section 530 includes a plurality of voltage dividingresistors 540 a and 540 b, a buffer 545, voltage sources 550 a and 550 b(also referred to as “voltage source 550”), and a plurality of drivers560 a to 560 d (also referred to as “driver 560”). The voltage dividingresistors 540 a and 540 b are connected in series between the first mainterminal and the second main terminal of the semiconductor device 120,and divide the inter-main-terminal voltage of the semiconductor device120 by a resistance ratio of a resistance value R1 of the voltagedividing resistor 540 a and a resistance value R2 of the voltagedividing resistor 540 b, thereby outputting a detection signalproportional to the inter-main-terminal voltage. Here, if theinter-main-terminal voltage of the semiconductor device 120 (thedrain-source voltage in this drawing) is Vds, the detection signal isR2/(R1+R2)·Vds.

The buffer 545 buffers and outputs a control signal input from theoutside. The buffer 545 may amplify and output the control signal inorder to drive the drivers 560 a to 560 d. In the present embodiment,the control signal instructs to turn off the semiconductor device 120 inthe case of a low level and to turn on the semiconductor device 120 inthe case of a high level. The voltage source 550 a outputs a thresholdvoltage Vth1 to be compared with the detection value of theinter-main-terminal voltage. The voltage source 550 b outputs athreshold voltage Vth2 to be compared with the detection value of theinter-main-terminal voltage.

The driver 560 a is connected to the buffer 545 and the voltage source550 a between the voltage dividing resistors 540 a and 540 b. The driver560 a is a driver with a comparator, and turns on the driving switch 520a with the control terminal of the driving switch 520 a at a low levelon condition that the detection signal of the inter-main-terminalvoltage is equal to or higher than the threshold voltage Vth1 in a casewhere the control signal input via the buffer 545 is at a low level. Ina case where the control signal is at a high level or in a case wherethe detection signal of the inter-main-terminal voltage is less than thethreshold voltage Vth1, the driver 560 a sets the control terminal ofthe driving switch 520 a to a high level and turns off the drivingswitch 520 a. Here, since the detection signal is a resistance dividedvoltage of the inter-main-terminal voltage of the semiconductor device120, the driver 560 a substantially compares the inter-main-terminalvoltage with a first threshold Th1 that is (R1+R2)/R2 times thethreshold voltage Vth1.

The driver 560 b is connected between the voltage dividing resistors 540a and 540 b and to the buffer 545. In a case where the control signal isat a low level, the driver 560 b sets the control terminal of thedriving switch 520 b to a low level and turns on the driving switch 520b. In a case where the control signal is at a high level, the driver 560b sets the control terminal of the driving switch 520 b to a high leveland turns off the driving switch 520 b.

As a result, in a period in which the semiconductor device 120 is turnedoff in response to switching of the control terminal from the high levelto the low level, the drivers 560 a and 560 b turn off the drivingswitch 520 a and turn on the driving switch 520 b while theinter-main-terminal voltage is less than the first threshold Th1starting from a state in which the inter-main-terminal voltage issubstantially 0, and drive the control terminal at a first drivecapability by the driving section 500. If the inter-main-terminalvoltage becomes equal to or higher than the first threshold Th1, thedrivers 560 a and 560 b turn on the driving switches 520 a and 520 b todrive the control terminal at a second drive capability.

Here, in a case where the driving switch 520 a is turned off and thedriving switch 520 b is turned on, the magnitude of the gate resistancebecomes a resistance value Rg2 of the resistor 510 b, whereas in a casewhere the driving switches 520 a and 520 b are turned on, the magnitudeof the gate resistance becomes a combined resistance valueRg1·Rg2/(Rg1+Rg2) by the parallel connection of the resistance valuesRg1 and Rg2 of the resistors 510 a and 510 b, and becomes smaller thanthe resistance value Rg2. Therefore, the second drive capability in acase where the driving switches 520 a and 520 b are turned on is higherthan the first drive capability in a case where the driving switch 520 ais turned off and the driving switch 520 b is turned on.

The driver 560 c is connected between the voltage dividing resistors 540a and 540 b and to the buffer 545. In a case where the control signal isat a high level, the driver 560 c sets the control terminal of thedriving switch 520 c to a high level and turns on the driving switch 520c. In a case where the control signal is at a low level, the driver 560c sets the control terminal of the driving switch 520 c to a low leveland turns off the driving switch 520 c.

The driver 560 d is connected to the buffer 545 and the voltage source550 b between the voltage dividing resistors 540 a and 540 b. The driver560 d is a driver with a comparator, and turns on the driving switch 520d with the control terminal of the driving switch 520 d at a high levelon condition that the detection signal of the inter-main-terminalvoltage is equal to or higher than the threshold voltage Vth2 in a casewhere the control signal input via the buffer 545 is at a high level. Ina case where the control signal is at a low level or in a case where thedetection signal of the inter-main-terminal voltage is less than thethreshold voltage Vth2, the driver 560 d sets the control terminal ofthe driving switch 520 d to a low level and turns off the driving switch520 d. Here, since the detection signal is a resistance divided voltageof the inter-main-terminal voltage of the semiconductor device 120, thedriver 560 d substantially compares the inter-main-terminal voltage witha second threshold Th2 that is (R1+R2)/R2 times the threshold voltageVth2.

As a result, in the period in which the semiconductor device 120 isturned on in response to the switching of the control terminal from thelow level to the high level, the drivers 560 c and 560 d turn on thedriving switches 520 c and 520 d while the inter-main-terminal voltageis equal to or higher than the second threshold Th2, and drive thecontrol terminal at a third drive capability by the driving section 500.When the inter-main-terminal voltage becomes less than the secondthreshold Th2, the drivers 560 c and 560 d turn on the driving switch520 c and turn off the driving switch 520 d to drive the controlterminal at a fourth drive capability by the driving section 500. Here,since the gate resistance in a case where the driving switch 520 c isturned on and the driving switch 520 d is turned off is larger than thegate resistance in a case where the driving switches 520 c and 520 d areturned on, the fourth drive capability is lower than the third drivecapability.

In this manner, the drive control section 530 can change the drivecapability of the control terminal by changing the magnitude of thecontrol resistance (gate resistance) connected between the controlterminal and the reference potential, that is, the magnitude of thecombined resistance. In place of the configuration illustrated in thisdrawing, the driving section 500 may have a control resistor by avariable resistor, and the drive control section 530 may change thedrive capability of the control terminal by changing the resistancevalue of the variable resistor of the driving section 500.

In addition, the driving section 500 may adopt a configuration includinga plurality of driving circuits in which a capacitor and the drivingswitch 510 are each connected in series between the reference potentialand the control terminal. In this case, the drive control section 530changes the drive capability of the control terminal by changing thecapacitance of the capacitor connected between the control terminal andthe first main terminal or the second main terminal.

Here, in a case where the same gate current is applied, as the combinedcapacitance of the capacitor connected between the control terminal andthe main terminal of the semiconductor device 120 increases, the changein the gate voltage is suppressed, and the drive capability of thedriving section 500 decreases. Therefore, in a case where a capacitor isused instead of the resistor 510 a, the driver 560 a turns on thedriving switch 520 a with the control terminal of the driving switch 520a at a low level on condition that the detection signal of theinter-main-terminal voltage is less than the threshold voltage Vth1 in acase where the control signal input via the buffer 545 is at a lowlevel. In a case where a capacitor is used instead of the resistor 510d, the driver 560 d turns on the driving switch 520 d with the controlterminal of the driving switch 520 d at a high level on condition thatthe detection signal of the inter-main-terminal voltage is less than thethreshold voltage Vth2 in a case where the control signal input via thebuffer 545 is at a high level.

FIG. 6 illustrates an operation waveform when the semiconductor device120 is turned off. Specifically, this drawing illustrates changes overtime indicated in the horizontal axis direction of each of the controlsignal, the connection state of the driving switch 520 a, the connectionstate of the driving switch 520 b, the control voltage (gate voltage) ofthe semiconductor device 120, the inter-main-terminal voltage VDS, and acurrent (drain current) ID flowing through the semiconductor device 120.

In a steady state in which the semiconductor device 120 is turned on,the control signal is at a high level, the driving switches 520 a and520 b are turned off, and the driving switches 520 c and 520 d areturned on. In this state, the inter-main-terminal voltage VDS of thesemiconductor device 120 is substantially 0 V, and the current IDrequired by the load 140 flows through the semiconductor device 120.

If the control signal changes from the high level to the low level, thedriving apparatus 130 starts a turn-off operation of the semiconductordevice 120. The driver 560 a turns off the driving switch 520 a during aperiod t1 in which the inter-main-terminal voltage VDS is less than thefirst threshold Th1. The driver 560 b turns on the driving switch 520 bwhen the control signal changes to the low level. The drivers 560 c and560 d turn off the driving switches 520 c and 520 d. As a result, thedrive control section 530 drives the control terminal of thesemiconductor device 120 at the first drive capability to lower thecontrol voltage of the control terminal.

If the control voltage drops to some extent, the semiconductor device120 starts turning off. Accordingly, the inter-main-terminal voltage VDSincreases, and after the period t1 elapses after the control signalchanges to the low level, the voltage VDS becomes equal to or higherthan the first threshold Th1. The driver 560 a turns on the drivingswitch 520 a in response to the inter-main-terminal voltage VDS becomingequal to or higher than the first threshold Th1. The semiconductordevice 120 decreases the current ID as indicated by the solid line inthe drawing in response to the start of turning-off, and sets thecurrent ID to 0 to be in the OFF state after a period t1+t2 after thecontrol signal changes to the low level.

According to the driving apparatus 130 of the present embodiment, in theturn-off operation of the semiconductor device 120, the drive capabilityof the driving section 500 is lowered during a period in which theinter-main-terminal voltage VDS changes from substantially 0 to thefirst threshold Th1 (that is, during a period in which theinter-main-terminal voltage VDS changes substantially by the voltagedifference of the first threshold Th1) as compared with the period afterthe inter-main-terminal voltage VDS becomes equal to or higher than thefirst threshold. Here, if the driving apparatus 130 does not have adriving circuit including the resistor 510 a and the driving switch 520a, and the control terminal of the semiconductor device 120 is drivenonly by the driving switch 520 b even after the inter-main-terminalvoltage VDS becomes equal to or higher than the first threshold Th1, thedecrease in the current ID is delayed as indicated by a broken line inthe drawing. In this case, as compared with a case where the controlterminal of the semiconductor device 120 is driven using both thedriving switch 520 a and the driving switch 520 b in a case where theinter-main-terminal voltage VDS becomes equal to or higher than thefirst threshold Th1, the turn-off period becomes longer as indicated byt11+t22 in the drawing, and the switching loss increases.

On the other hand, according to the driving apparatus 130 of the presentembodiment, while the drive capability of the driving section 500 islowered during the period t1 in which the inter-main-terminal voltageVDS changes by the reference voltage difference, the drive capability ofthe driving section 500 is increased during the period t2 in which theinter-main-terminal voltage VDS does not relatively change. Here, as thechange rate of the inter-main-terminal voltage VDS increases, thevibration accompanying the turn-off of the semiconductor device 120increases. However, the driving apparatus 130 lowers the drivecapability of the driving section 500 in the period t1 in which theinter-main-terminal voltage VDS changes largely to suppress the changerate of the voltage VDS, thereby efficiently suppressing the generationof vibration.

FIG. 7 illustrates an operation waveform at the time of turn-on of thesemiconductor device 120. Specifically, this drawing illustrates changesover time in the horizontal axis direction of each of the controlsignal, the connection state of the driving switch 520 d, the connectionstate of the driving switch 520 c, the control voltage (gate voltage) ofthe semiconductor device 120, the inter-main-terminal voltage VDS, and acurrent (drain current) ID flowing through the semiconductor device 120.

In a steady state in which the semiconductor device 120 is turned off,the control signal is at a low level, the driving switches 520 a and 520b are turned on, and the driving switches 520 c and 520 d are turnedoff. In this state, the inter-main-terminal voltage VDS of thesemiconductor device 120 is substantially a power source voltagegenerated by the electrolytic capacitor 110, and no current flowsthrough the semiconductor device 120.

If the control signal changes from the low level to the high level, thedriving apparatus 130 starts a turn-on operation of the semiconductordevice 120. The drivers 560 c and 560 d turn on the driving switches 520c and 520 d while the inter-main-terminal voltage VDS is equal to orhigher than the second threshold Th2. The drivers 560 a and 560 b turnoff the driving switches 520 a and 520 b. As a result, the drive controlsection 530 drives the control terminal of the semiconductor device 120at the third drive capability to increase the control voltage of thecontrol terminal.

If the control voltage increases to some extent, the semiconductordevice 120 starts turning on. Accordingly, the inter-main-terminalvoltage VDS drops, and after the period t3 elapses after the controlsignal changes to the high level, the voltage VDS becomes less than thesecond threshold Th2. The driver 560 d turns off the driving switch 520d in response to the inter-main-terminal voltage VDS becoming less thanthe second threshold Th2. The semiconductor device 120 drops theinter-main-terminal voltage VDS as indicated by the solid line in thedrawing in response to the start of turning-on, and sets theinter-main-terminal voltage VDS to substantially 0 after a period t3+t4after the control signal changes to the high level. In addition, thesemiconductor device 120 increases the current ID as indicated by thesolid line in the drawing in response to the start of turning-on, andsets the current ID as a steady current near the time point when theperiod t3+t4 elapses after the control signal changes to the high level.

According to the driving apparatus 130 of the present embodiment, in theturn-on operation of the semiconductor device 120, the drive capabilityof the driving section 500 is lowered during a period in which theinter-main-terminal voltage VDS changes from the second threshold Th2 tosubstantially 0 (that is, during a period in which theinter-main-terminal voltage VDS changes substantially by the voltagedifference of the second threshold Th2) as compared with the periodafter the inter-main-terminal voltage VDS becomes equal to or higherthan the second threshold. Here, if the driving apparatus 130 does nothave a driving circuit including the resistor 510 d and the drivingswitch 520 d, and the control terminal of the semiconductor device 120is driven only by the driving switches 520 b and 520 c even while theinter-main-terminal voltage VDS becomes equal to or higher than thesecond threshold Th2, the decrease in the inter-main-terminal voltageVDS and the increase in the current ID are delayed as indicated by abroken line in the drawing. In this case, as compared with a case wherethe control terminal of the semiconductor device 120 is driven usingboth the driving switch 520 c and the driving switch 520 d while theinter-main-terminal voltage VDS is equal to or higher than the secondthreshold Th2, the turn-on period becomes longer as indicated by t33+t44in the drawing, and the switching loss increases.

On the other hand, according to the driving apparatus 130 of the presentembodiment, while the drive capability of the driving section 500 islowered during the period t4 in which the inter-main-terminal voltageVDS changes by the reference voltage difference, the drive capability ofthe driving section 500 is increased during the period t3 in which theinter-main-terminal voltage VDS does not relatively change. Here, as thechange rate of the inter-main-terminal voltage VDS increases, thevibration accompanying the turn-off of the semiconductor device 120increases. However, the driving apparatus 130 lowers the drivecapability of the driving section 500 in the period t4 in which theinter-main-terminal voltage VDS changes largely to suppress the changerate of the voltage VDS, and suppresses the reduction rate of theresistance value of the semiconductor device 120 to increase the dampingresistor Rd, thereby efficiently suppressing the generation ofvibration.

At least one of the first threshold Th1 to be compared with theinter-main-terminal voltage VDS during the turn-off period and thesecond threshold Th2 to be compared with the inter-main-terminal voltageVDS during the turn-on period may be 60% or more and less than 100%, or80% or more and less than 95% of the inter-main-terminal voltage in thesteady state in which the semiconductor device 120 is turned off. Inaddition, the first threshold Th1 and the second threshold Th2 may bethe same value or different values.

FIG. 8 illustrates an example of transient changes in current andvoltage at the time of turn-off of when the semiconductor device. Inthis drawing, the same conditions as those in FIG. 4 are applied exceptthat the resistance (gate resistance) between the driving apparatus 130b and the semiconductor device 120 b is increased from 0.1Ω to 2Ω duringthe period in which the inter-main-terminal voltage changes by thereference voltage difference.

In FIG. 4, local high-frequency vibrations of the current Id and thevoltage Ids by the LC circuit due to the inductance Ls2 and the junctioncapacitance Cos are observed at the timing when the semiconductor device120 b is turned off at 15.0 μs on the horizontal axis. On the otherhand, in this drawing, such high-frequency vibration can be suppressed.The driving apparatus 130 only needs to increase the gate resistanceduring the period in which the inter-main-terminal voltage changes bythe reference voltage difference, and may increase the gate resistancetwice or more, for example.

How much the drive capability of the driving apparatus 130 is loweredduring the period in which the inter-main-terminal voltage changes bythe reference voltage difference, that is, for example, how much thegate resistance is increased may vary depending on the magnitude of thewiring inductance Ls2 or the like. Therefore, the manufacturer of thesemiconductor apparatus 115 or the user of the semiconductor apparatus115 may determine the drive capability of the driving apparatus 130using the simulation result of the semiconductor apparatus 115 or thetest result of the semiconductor apparatus 115. In addition, the drivingapparatus 130 may include a setting memory or the like in which thedrive capability of the driving apparatus 130 during a period in whichthe inter-main-terminal voltage changes by the reference voltagedifference can be set from the outside, or the drive capability of thedriving apparatus 130 may be switched according to the setting value.

Although the present invention has been described using the embodiments,the technical scope of the present invention is not limited to the scopedescribed in the above embodiments. It is apparent to those skilled inthe art that various modifications or improvements can be made to theabove embodiments. It is apparent from the description of the claimsthat a mode to which such a change or improvement is added can also beincluded in the technical scope of the present invention.

It should be noted that the order of execution of each processing suchas operations, procedures, steps, and stages in the apparatuses,systems, programs, and methods illustrated in the claims, thespecification, and the drawings can be realized in any order unless“before”, “prior to”, or the like is specifically stated, and unless theoutput of the previous processing is used in the later processing. Evenif the operation flow in the claims, the specification, and the drawingsis described using “first”, “next”, and the like for convenience, itdoes not mean that it is essential to perform in this order.

EXPLANATION OF REFERENCES

-   100: power apparatus;-   110: electrolytic capacitor;-   115: semiconductor apparatus;-   120 a, 120 b: semiconductor device;-   130 a, 130 b: driving apparatus;-   140: load;-   150: inductor;-   180: snubber;-   185: resistor;-   190: capacitor;-   280 a, 280 b: snubber;-   285 a, 285 b: resistor;-   290 a, 290 b: capacitor;-   500: driving section;-   510 a, 510 b, 510 c, 510 d: resistor;-   520 a, 520 b, 520 c, 520 d: driving switch;-   530: drive control section;-   540 a, 540 b: voltage dividing resistor;-   545: buffer;-   550 a, 550 b: voltage source;-   560 a, 560 b, 560 c, 560 d: driver

1. A driving apparatus comprising: a driving section configured to drivea control terminal of a semiconductor device according to a controlsignal input from an outside, the semiconductor device including a firstmain terminal, a second main terminal, and the control terminal that isconfigured to control a connection state between the first main terminaland the second main terminal that are connected in parallel with asnubber; and a drive control section configured to lower a drivecapability of the driving section during a period in which aninter-main-terminal voltage between the first main terminal and thesecond main terminal changes by a predetermined reference voltagedifference owing to switching of the semiconductor device, compared withother at least some periods.
 2. The driving apparatus according to claim1, wherein in a period in which the semiconductor device is turned off,the drive control section drives the control terminal at a first drivecapability by the driving section while the inter-main-terminal voltageis less than a first threshold, and drives the control terminal at asecond drive capability higher than the first drive capability by thedriving section when the inter-main-terminal voltage becomes equal to orhigher than the first threshold.
 3. The driving apparatus according toclaim 2, wherein in a period in which the semiconductor device is turnedon, the drive control section drives the control terminal at a thirddrive capability by the driving section while the inter-main-terminalvoltage is equal to or higher than a second threshold, and drives thecontrol terminal at a fourth drive capability lower than the third drivecapability by the driving section when the inter-main-terminal voltagebecomes less than the second threshold.
 4. The driving apparatusaccording to claim 3, wherein the first threshold and the secondthreshold are 60% or more and less than 100% of the inter-main-terminalvoltage in a steady state in which the semiconductor device is turnedoff.
 5. The driving apparatus according to claim 3, wherein the firstthreshold and the second threshold are 80% or more and less than 95% ofthe inter-main-terminal voltage in a steady state in which thesemiconductor device is turned off.
 6. The driving apparatus accordingto claim 4, wherein the first threshold and the second threshold are 80%or more and less than 95% of the inter-main-terminal voltage in a steadystate in which the semiconductor device is turned off.
 7. The drivingapparatus according to claim 3, wherein the first threshold and thesecond threshold are the same values.
 8. The driving apparatus accordingto claim 4, wherein the first threshold and the second threshold are thesame values.
 9. The driving apparatus according to claim 5, wherein thefirst threshold and the second threshold are the same values.
 10. Thedriving apparatus according to claim 1, wherein the drive controlsection changes a drive capability of the control terminal by changingat least one of a magnitude of a resistance of a resistor connectedbetween the control terminal and a reference potential or a capacitanceof a capacitor connected between the control terminal and the first mainterminal or the second main terminal.
 11. The driving apparatusaccording to claim 2, wherein the drive control section changes a drivecapability of the control terminal by changing at least one of amagnitude of a resistance of a resistor connected between the controlterminal and a reference potential or a capacitance of a capacitorconnected between the control terminal and the first main terminal orthe second main terminal.
 12. The driving apparatus according to claim3, wherein the drive control section changes a drive capability of thecontrol terminal by changing at least one of a magnitude of a resistanceof a resistor connected between the control terminal and a referencepotential or a capacitance of a capacitor connected between the controlterminal and the first main terminal or the second main terminal. 13.The driving apparatus according to claim 1, wherein the driving sectionincludes a plurality of driving circuits in which a resistor or acapacitor, and a driving switch are each connected in series between areference potential and the control terminal, and the drive controlsection changes a drive capability of the driving section by switchingthe driving switch of each of the plurality of driving circuits.
 14. Thedriving apparatus according to claim 2, wherein the driving sectionincludes a plurality of driving circuits in which a resistor or acapacitor, and a driving switch are each connected in series between areference potential and the control terminal, and the drive controlsection changes a drive capability of the driving section by switchingthe driving switch of each of the plurality of driving circuits.
 15. Thedriving apparatus according to claim 3, wherein the driving sectionincludes a plurality of driving circuits in which a resistor or acapacitor, and a driving switch are each connected in series between areference potential and the control terminal, and the drive controlsection changes a drive capability of the driving section by switchingthe driving switch of each of the plurality of driving circuits.
 16. Thedriving apparatus according to claim 1, wherein the semiconductor deviceis a SiC-MOSFET or a SiC-IGBT.
 17. The driving apparatus according toclaim 2, wherein the semiconductor device is a SiC-MOSFET or a SiC-IGBT.18. The driving apparatus according to claim 3, wherein thesemiconductor device is a SiC-MOSFET or a SiC-IGBT.
 19. A semiconductorapparatus comprising: the semiconductor device; and the drivingapparatus according to claim 1 that is configured to drive a controlterminal of the semiconductor device.
 20. A driving method comprising:driving, by a driving section, a control terminal of a semiconductordevice according to a control signal input from an outside, thesemiconductor device including a first main terminal, a second mainterminal, and the control terminal that is configured to control aconnection state between the first main terminal and the second mainterminal that are connected in parallel with a snubber; and lowering adrive capability of the driving section during a period in which aninter-main-terminal voltage between the first main terminal and thesecond main terminal changes by a predetermined reference voltagedifference owing to switching of the semiconductor device, compared withother at least some periods.